Khan said he would consult the London Resilience Forum, which plans responses to disasters such as the Grenfell Tower Fire, about the implications for Britain of crashing out of the European Union without a deal, saying that such a “catastrophic” outcome looked more likely than ever.

Britain is due to leave the EU in March 2019, and with time running out to secure agreement on future ties, both British and European politicians are warning of the increased chances of a “no-deal” Brexit.

“Even ministers now admit that crashing out of the EU with no deal is now more likely than ever,” Khan said in a statement. “We are now left with no choice but to plan for a no-deal scenario.”

Foreign Secretary Jeremy Hunt told ITV News in an interview on Thursday that leaving the EU in a “messy, ugly divorce” would be a mistake that Britain would “regret for generations”, although he tweeted on Friday to clarify that he believed Britain would “survive and prosper without a deal”.